1. Field of the Invention
This invention relates to belts and, more particularly, to a conveying belt having a treated surface which contacts and conveys objects as the conveying belt is advanced. The invention is also directed to a method of forming the conveying belt.
2. Background Art
Conveying belts are used in a wide range of environments. The conveying belt has an exposed surface which engages objects and through frictional forces generated between the conveying belt and objects in contact therewith causes conveyance of the objects as the conveying belt is advanced. Designers of this type of belt must consider a number of different objectives. The conveying surface must positively convey objects in operation. At the same time, the conveying surface must be resistant to adherence of the conveyed objects so that unimpeded separation between the conveying belt and objects occurs at the appropriate time. The conveying surface should also be resistant to adherence of other foreign matter, particularly that which leaches or leaks from the objects conveyed.
To accomplish the above objectives, it is known to use a canvas material as the top exposed layer on the conveying belt and to coat the canvas with a fluororesin. Conveying belts so treated generally have good stability at both high and low temperatures, are chemically inactive, have a low frictional coefficient between the conveying surface and objects being conveyed, and facilitate stripping of material from the belt surface. Conveying belts with a fluororesin treated canvas conveying surface have proven to be highly useful in fields in which various operations are carried out directly on the conveying belt, and particularly in an environment where a wide belt having a large conveying operating surface is used. One exemplary conveying belt is shown in Japanese Provisional Publication No. 7-60877. In this patent document, a treated belt is shown as a component of a corrugated board manufacturing machine.
In FIG. 5 herein, a corrugated board manufacturing machine, incorporating a belt such as shown in Japanese Provisional Publication No. 7-60877, is shown at 10. A web 12 is continuously directed between a pair of meshing, toothed rolls 14, 16 which impress a corrugated, fluted pattern into the web 12. A sizing machine 18 applies starch sizing material to the apices 20 of the flutes on one side 22 of the web 12. An endless belt 24 is trained around a pair of spaced pulleys 26, 28 downstream of the sizing machine. The relative position of the pulleys 26, 28 is selected to produce a predetermined tension on the belt 24. The unsupported region of the belt 24 between the pulleys 26, 28 is biasably urged over a portion of the roll 16. A liner 30 is continuously advanced between the belt 24 and roll 16 and is pressed by the belt 24 against the advancing web 12 to effect adherence between the liner 30 and the apices 20 on the web 12. The completed corrugated board 32 exits from between the pulley 26 and roll 16. Heat is imparted to the web 12 and liner 30 at a location between the belt 24 and roll 16 to evaporate water in the web 12 and thereby assure accurate flute formation on the web 12.
The exposed belt surface 34, which is commonly canvas, is treated with a blend of powdery fluororesin and a heat resistant elastomer in relatively large quantities to facilitate separation of the completed board 32 from the exposed conveying surface 34 of the belt 24. This treatment also facilitates removal of foreign matter such as adhesive that leaks from the board 32 to the belt surface 34.
While the fluororesin treatment reduces the coefficient of friction between the belt 24 and board 32, the fluororesin compromises the adhesion of the canvas layer defining the exposed surface 34 on the belt 24 with other belt components/layers. As a result, there is a tendency of the canvas layer to peel, which compromises the durability and longevity of the belt 24.
The presence of the heat resistant elastomer in the treatment composition also increases surface friction between the belt surface 34 and objects being conveyed. As a result, separability may be compromised. There may also be a tendency of foreign matter, such as adhesive, to more aggressively adhere to the conveying surface 34.